Portable ultrasonic detectors are frequently used in inspection applications. Typical objects of inspection may include welded steel parts for example steel tubes. The ultrasonic detector may be coupled by a grease, an oil or water to the part, and the inspector may move the detector in various zigzag type movements to areas of interests such as a weld or a corroded backwall, or away from it to other areas. Using such an instrument, flaws in the part or bad welds may be observed. As the movement of the detector-is random and undetermined, it is often difficult to image the detected failures in relation to the dimensions and design features of the part and the probe position. As the parts may be complex, for example tubes, T-joints, and so on, the geometry of the parts may increase the difficulty of inspecting such parts and identifying the coordinates of any detected flaws in dependence of the probe position.